Mayweather to fight Japanese kickboxer Nasukawa in December

Mayweather's exhibition vs. Japanese kickboxer back on

Floyd Mayweather of the U.S. speaks during a press conference in Tokyo, Monday, Nov. 5, 2018. Mayweather said he has signed to fight Japanese kickboxer Tenshin Nasukawa for a bout promoted by Japan's RIZIN Fighting Federation on Dec. 31 in Saitama, north of Tokyo. (Katsuya Miyagawa/Kyodo News via AP)

TOKYO (AP) -- Floyd Mayweather is planning on fighting Japanese kickboxer Tenshin Nasukawa on Dec. 31 in Saitama, north of Tokyo.

The 41-year-old Mayweather is 50-0 in his boxing career but has never fought professionally under MMA rules. Although he did have a lucrative win over MMA fighter Conor McGregor last year.

Japanese promoter the RIZIN Fighting Federation on Monday said rules and the weight class for the bout have not been set.

''We still have some work to do,'' said Nobuyuki Sakakibara, the RIZIN chairman.

The 20-year-old Nasukawa, speaking at a news conference alongside Mayweather, called it ''probably the biggest event of my life so far.''

He also vowed to end Mayweather's long string of victories.

''Nobody has defeated my opponent in the past, and I would like to be the man who makes history,'' Nasukawa said, speaking through an interpreter. ''My punch can change history. And I will show that to you. So please stay tuned.''